Magnetron tube with axially movable tuning means



Oct. 27, 1964 M. R. BOYD ETAL MAGNETRON TUBE WITH AXIALLY MOVABLE TUNING MEANS Filed Oct. 27, 1954 2 Sheets-Sheet 1 Mall-#7025 MEIFLf A? B YD fiasierfi EMPDS' Oct. 27, 1964 M. R. BOYD ETAL MAGNETRON TUBE WITH AXIALLY MOVABLE TUNING MEANS Filed Oct. 27, 1954 IIHI JILEF FREOUENCV- K/L OMEGAC vcz. 55 N TUNER TURNS 2 Sheets-Sheet 2 /NVEN7'0/?S MERLE R 501 0 ROBERT E. EDWARDS United States Patent 3,154,717 MAGNE'I'RON TUBE WITH AXIALLY hdflVABLE TUNING MEANS Merle R. Boyd, Auhnrndale, and Robert E. Edwards,

Boston, Mass, assignors to Raytheon Company, a corporation of Delawme Filed Oct. 27, 1954, Ser. No. 455,618 12 Claims. (Cl. 315-3961) This invention relates to tunable electron discharge devices and more particularly to tunable oscillation generating devices of the magnetron type.

This invention provides for flexible control of the tuning of a magnetron and specifically provides means for tuning a magnetron over a wider frequency range than magnetrons of the prior art without interference with extraneous tuner resonances inherent in tunable magnetrons and for achieving a faster tuning rate than that realized with the ordinary inductive tuner.

Another feature of the invention is the introduction of capacitive tuning in a portion of the cavity resonators where radio frequency voltage is relatively low, thereby permitting satisfactory operation in high power tubes of the pulsed type. Finally, the tuning structure is so positioned within the cavity resonators that mechanical interference between the tuner and the straps on the anode structure is avoided.

As is well known in the magnetron art, a magnetron anode structure consists of several more or less radially disposed anode segments extending from a generally cylindrical wall portion. Each pair of adjacent anode segments and the portion of the anode structure lying therebetween form the boundary of a cavity resonator whose resonant frequency is a function of the geometry of the elements bounding said resonator. The cavity resonators each have a distributed capacitance and inductance, but for all practical purposes the portion of each cavity resonator adjacent the cathode, sometimes referred to as the front portion of the resonator, is predominantly capacitive, while the inductance is more or less concentrated in that portion of the cavity resonator furthest removed from the cathode and sometimes referred to as the rear portion of the resonator. For example, with sectorshaped cavities, such as appear in anodes of the vane type, the capacitive region is considered to extend from the vane tips facing the cathode approximately midway back to the anode cylinder wall and the inductive region is considered to consist of the remainder of the resonator. With a hole-and-slot type anode block having keyholeshaped cavity resonators, the capacitive region is considered to exist almost entirely within the slot between parallelly disposed portions of adjacent anode segments, while the inductive region is concentrated largely within the hole or cylindrically shaped portion of the resonator remote from the cathode. The electric field is greater in the capacitive or forward portion of each resonator while the magnetic field is greater in the inductance or rear portion. The inductive portion of the resonator, as compared with the capacitive region thereof, is a high current region. This invention, of course, is applicable to any magnetron regardless of the type of anode structure.

The standard inductive magnetron tuning system of the prior art comprises a plurality of tuning fingers, each of which extends into the rear or inductive portion of a corresponding resonator. When such tuning fingers are inserted within a cavity resonator the surface to volume 3,154,717. Patented Oct. 27, 1964 circuit thus is decreased as the fingers penetrate further into each resonator, consequently increasing the frequency of oscillation of the magnetron. Such inductive tuning systems, as well as capacitive tuning systems, are characterized inherently by extraneous tuner resonances or modes which interfere with operation of the magnetron in the desired mode, usually the 11' mode. A major type of resonance interference is an end cavity resonance at the tuner end of the anode structure resulting from the capacitance existing between the tuner and the magnetron resonator system. This effect is most pronounced when the tuner fingers are approaching the anode structure and while the tuner fingers are inserted but slightly within the cavity resonators.

In accordance with this invention the possibility of tuning to the extraneous resonances instead of the desired resonance is reduced by modifying the inductive tuning fingers of the prior art so that a portion of each tuning finger adjacent the end thereof which is first inserted into the resonator provides an open circuit to any current which would otherwise be induced in that portion of the finger. This modification may take the form of a longitudinal slot or other discontinuity in the aforesaid portion. The change of inductance of the resonator resulting from the circulating current induced in the finger is consequently eliminated or substantially reduced, depending upon the character of the discontinuity. There is a capacity between the walls of the cavity resonator and the modified portion of the tuner finger so that the latter portion serves as a capacitive tuner.

When the tuner fingers are first inserted into the cavity resonators, therefore, the tuning is predominantly capaci tive and the magnetron operating frequency decreases with tuner penetration. The tuning gradually becomes less capacitive as the unmodified portion of the tuning fingers enters the cavity resonators until the penetration of the unmodified portion of the fingers into the resonators becomes sufiicient to cause the inductance efiect of the tuner to predominate over the capacitive effect. Further penetration of the tuner results in an increase in frequency with an increase in tuner penetration. By the time that the resultant tuning changes from capacitive to inductive, the competing extraneous resonance or resonances are well displaced from the region required by the desired mode.

Since the introduction of the modified portion of the tuner into the anode resonant system first causes a decrease in frequency prior to an increase in frequency at the change-over point at which tuning becomes predominantly inductive, a greater tuning range is attained than can be realized by the use of the regular inductive tuner of the prior art. Furthermore, because the capacitive effect changes at the same time that the inductive effect changes over a portion of the range of tuner penetration, a faster tuning rate may be obtained by applicants tuner than is possible with a simple unmodified inductive tuner.

In the drawing:

FIG. 1 is a longitudinal sectional view taken tln'ough the center of a tunable magnetron in accordance with the invention;

FIG. 2 is a fragmentary end view showing a portion of the anode structure and tuning fingers of the magnetron of FIG. 1;

FIG. 3 is a perspective view of a portion of the tuner assembly used in the device of FIG. 1;

FIG. 4 is a detailed view showing a fragment of one of the fingers of the tuner assembly of FIG. 3;

FIG. 5 is a fragmentary end view showing a portion of a hole-and-slot type anode structure including a modification of the tuner assembly of FIGS. 1 to 3;

FIG. 6 is a fragmentary perspective view of a modifia I H 3,154,717

3 cation of the tuner assembly of FIG. 3 as used in the device of FIG. 5;

FIG. 7 is a fragmentary view showing the radio frequency current distribution in the inductive portion of a tuner, such as that of FIGS. 5 and 6; and

FIG. 8 is a performance chart showing the variation of magnetron operating frequency with tuner penetration in the anode structure of the magnetron of FIGS. 1 and 2.

Referring to FIGS. 1 to 4 of the drawing, reference numeral 11 designates an electron discharge device of the magnetron type including an anode structure 12, a cathode structure 13, magnetic means 14 for producing a magnetic field in a direction normal to the electric field between the cathode and anode structures and a tuner assembly 15 for varying the magnetron operating frequency.

Anode structure 12 comprises an integral block made of an electrically conductive material, such as copper, and includes a toroidal wall 18 from whose interior surface extends a plurality of radially disposed anode segments or vanes 19. Each pair of adjacent segments and the portion of cylindrical wall 18 lying therebetween form a cavity resonator 20 which opens into the space between the anode and cathode structures. The cavity resonators are substantially identical in size and configuration and together form a unitary resonant system.

Anode block 12 also is provided with two sets of 22 and 23 of annular conducting straps, each including two concentrically arranged elements interconnecting alternate anode segments, in the well known manner. The two sets of straps are located at opposite ends of the anode block, as shown in FIG. 1. Any number of sets of straps may be used depending largely upon the axial length of the anode segments.

Anode structure 12 is closed at one end by an end plate 24 hermetically sealed to the anode structure along junction 25. The other end of the anode structure is closed by means of an enlarged magnetic pole piece 26 brazed or otherwise hermetically sealed to the anode wall 18 along junction 27 and apertured to receive one end of cathode structure 13.

Cathode structure 13 is coaxially arranged with respect to anode structure 12 and includes a cathode sleeve 28 provided with a reduced portion 28 coextensive with the anode segments 19; the reduced portion 28' is coated with an electron-emissive material 29. A filamentary type heater 38 is inserted within a bore 31 in cathode sleeve 28 and one end of said heater is connected to the cathode sleeve. The details of the supporting means for the cathode structure and the means for connecting the cathode heater to a power supply do not form a part of th invention and have been omitted for reasons of simplicity. These cathode details are fully shown and described in United States Patent 2,624,861 of W. C. Brown, issued January 6, 1953.

Magnetic field producing means 14 includes, in addition to upper pole piece 26 already referred to, a lower pole piece 33 of opposite polarity. Pole piece 33 is apertured to receive cathode structure 13 and is hermetically sealed to the anode end plate 24 along junction 34. Pole pieces 26 and 33 are afiixed to opposite ends of a U- shaped magnet, omitted from the drawing in the interest of clarity. The relationship of the U-magnet to the pole pieces of the magnetron is shown in the aforesaid patent of W. C. Brown. a

Radio frequency energy is extracted from one or more cavity resonators of the magnetron by appropriate output coupling means, not shown, such as a wave guide positioned adjacent a slot or slots in the anode wall. Such energy coupling means are well known in the art and may be positioned at any point about the periphery of the magnetron anode structure.

Referring particularly to FIG. 3, the tuner structure 15 for magnetron 11 includes an annular base 38 from which depends a plurality of peripherally spaced tuning members or fingers 40. These fingers are preferably of tubular construction, for reasons which will become more apparent subsequently. Fingers 40 pass through apertures 42 in upper pole piece 26, as shown in FIG. 1. The upper portions 49a of tuner fingers 40 nearest base 38 are generally cylindrical while the lower or effective portions 4012 which are adapted to extend in and out of the cavity resonators are extruded into a more or less semi-cylindrical configuration, as clearly shown in FIG. 3, in order to provide adequate clearance between the fingers and both sets of straps and so that the effective portion of said fingers lie in the inductive or high current region of the corresponding resonators. Furthermore, because of the tear-shaped configuration of the cavity resonators of a magnetron, such as that shown in FIGS. 1 and 2, there may sometimes be insufficient space near the front of the resonators to accommodate a cylindrical tuning finger unless the diameter of said fingers is appreciably reduced and the tuning efiect consequently diminished.

A portion of each tuner finger adjacent the end thereof remote from the base is provided with a longitudinally extending slot 45. The slotted portion 45 of each tuning finger 40 is substantially capacitive while the continuous unslotted portion is substantially inductive, as shown by the reference characters C and L respectively, of FIG. 4. The length of slots 45 depends upon the amount of capacitive tuning desired to produce a given tuning curve. The reason for the existence of the capacitive and inductive portions of the tuning fingers is pointed out in connection with FIG. 7 to be referred to later. The slots 45 in tuner fingers 40 are preferably oriented so that the slots are at the rearmost part of the cavity resonator, thus minimizing the tendency toward arcing at the slot. Base 38 of tuner structure 15 is affixed to an adjusting rod 47 and is slidably mounted within a sleeve 49 hermetically sealed to pole piece 26. Adjusting rod 47 may, for example, be connected to a mechanism, not shown, such as illustrated in the aforesaid Brown patent which is capable of transforming calibrated rotary motion of a rotating member into reciprocating axial motion, whereby the axial position of the tuner and, hence, the degree of penetration of the tuner fingers into the corresponding cavity resonators, are varied by any desired amount as a function of the number of turns of said rotating member. Any means for attaining the desired amount of axial movement of the tuner fingers, may, of course, be within the confines of the subject invention. In order to maintain a vacuum within the magnetron envelope, a flexible hermetic seal is provided by means of a bellows 50 having one end securely attached to base 38 of tuner assembly 15 and the other end, not shown, connected to the inner wall of sleeve 49.

A hole and slot type anode block is shown in FIG. 5 which differs from the vane type anode block of FIGS. 1 and 2 principally in that there is a more distinct boundary between the predominantly inductive and predominantly capacitive regions of the resonators. In the device of FIG. 5 the predominantly capacitive region of each resonator 20 is bound by a comparatively elongated parallel portion of the anode block 12, while the predominantly inductive region is substantially cylindrical in configuration. For this reason the effective portion 40b of each tuner finger 40 may be cylindrical throughout its length, as clearly shown in FIG. 6, so as to occupy a substantial portion of the arcuate inductive region of a corresponding resonator 20.

In FIG. 7 the inductive effect in a tuner having a finger such as finger 40 of FIG. 3 or finger 40' of FIG. 6 is illustrated. Although the tuner finger 40' as shown in FIG. 7 is a cylindrical finger and is inserted in a hole and slot type anode, it should be understood that the principles of operation are equally applicable to a magnetron having a vane type anode and a semi-cylindrical tuning finger, such as that shown in FIGS. 1 and 2. In either case, the radio frequency magnetic field is concentrated in the arcuate portion of the cavity resonators remote from the cathode and its pattern at a given instant of time is indicated by crosses. A circulating radio frequency current flows adjacent the periphery of the cavity resonators, whether of the hole and slot type or any other type, in a manner indicated by the arrows. A current of opposite phase is inducted in the continuous inductive portion of the tuner finger as indicated generally in FIG. 7. This induced current is concentrated mainly at the surface of the tuner finger.

When the slotted portion of the tuner finger of FIG. 7 is inserted within cavity resonator 20, it is obvious that there can be no current induced in the tuner finger since there is no closed path for the flow of current. For this reason the inductive effect is negligible during the time that the slotted or capacitive portion only of the tuner finger is inserted within the corresponding resonator; the capacitance between the tuner and the walls of the cavity resonator now comes into full play. As the tuner penetrates further into the resonator, more and more of the inductive portion of the tuner finger is effective until, finally, the tuning effect becomes predominantly induc tive. Further insertion of the tuner fingers beyond the point at which the inductive effect predominates results in continuous inductive tuning as in the case of the standard inductive tuner. The length of the slot 45 in the tuner fingers obviously must be less than the depth of the magnetron cavity resonators, that is, the dimension of the cavity resonators parallel to the longitudinal axis of the tube, else the tuning would be capacitive at all times.

The tuning fingers 40 and 40' need not be limited to the respective semi-cylindrical and cylindrical configurations heretofore described. The principal requirement in this respect is that the finger be capable of axial movement within the predominantly capacitive portion of the corresponding anode resonator. The more nearly the periphery of each tuner finger conforms to that of the resonator wall in the capacitive regions, however, the larger becomes the capacity between the tuning finger and the resonant cavity wall and the greater the capacitive tuning effect for small tuner penetrations. Likewise, the closer the spacing between the tuner finger and the resonator wall, the greater the inductive tuning efi'ect becomes for greater tuner penetrations.

Although a. tuner finger of tubular construction is preferable in that a discontinuity may be readily provided therein, the invention is not limited to tuners of tubular construction. For example, where a less ellicient tuner is adequate, the tuner fingers may each be made of solid construction, provided a sufiiciently deep slot or other discontinuity is located adjacent one end of the tuner. In this case, of course, a very small induced circulating current would exist at all times; the inductance, however, may still be reduced to the extent that the capacitance between the tuner finger and the wall of the corresponding resonator would be predominant.

The effect of the tuner penetration, represented by a certain number of tuner turns, upon the operating frequency of a magnetron of the type shown in FIGS. 1 and 2 is illustrated in FIG. 8. In FIG. 8 a tuning curve 51 for an inductive tuner of the conventional type and a tuning curve 52 for a slotted tuner constructed in accordance with the invention are shown. In addition, an extraneous tuner resonance is indicated by curve 53. In the ordinary inductive tuner the frequency increases throughout the tuning range, as shown by curve 51. Interference occurs with a tuner resonance at some low value of tuner penetration, as shown at point 2:. Although only one extraneous resonance is shown in FIG. 8, several extraneous resonances may occur in some instances, particularly if the tuner fingers are of an unequal length or differ in instantaneous degree of penetration. Since operation beyond point x is necessary to avoid interference with the tuner resonance or resonances, a limitation is thus placed upon the permissible frequency tuning range. For example, the effective tuning range for a regular inductive tuner is from about 2700 megacycles to 3,060 megacycles.

With the slotted tuner of the invention, however, the operating frequency is decreased at low penetrations and does not increase unt l the inductive effect of the tuner predominates, as at point y on curve 52. From point y to point z the operating frequency increases substantially linearly from a value of about 2575 megacycles to 3060 megacycles. The difierences between the regular inductive tuner and the slotted LC tuner of the subject invention are evident from an inspection of FIG. 8. Firstly, the extraneous resonance is well removed from the inductive portion of the slotted LC tuner curve 52; that is, there is no possibility of interfering tuner resonances over a tuner penetration range productive of linear inductive tuning. Secondly, a faster tuning rate is achieved with the slotted LC tuner of the invention than in the case of the simple inductive tuner of the prior art. For example, in the region between approximately 10 and 45 tuner turns, the frequency is varied from approximately 2575 megacycles to 3,000 megacycles, corresponding to the tuning range of 425 megacycles. In comparison, use of the regular inductive tuner will result in a corresponding variation in frequency from about 2700 megacycles to 3025 megacycles or a tuning range of 325 megacycles. The increase in tuning range through use of the capacitive extension on the inductive tuner according to the invention is of the order of 30%.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators and a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure and movable with respect thereto, said members each having an inductive portion and a capacitive portion forming an extension of said inductive portion.

2. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators each having a predominantly capacitive region adjacent one end thereof and a predominantly inductive region adjacent the other end thereof, a tuning structure including a plurality of axially extending electrically conductive members each having a capacitive portion and an inductive portion, and means for effecting movement of said capacitive and inductive portions of each of said members within said predominantly inductive region of corresponding resonators in the order named.

3. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators, a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure, said members including an inductive portion and a capacitive portion, means for effecting movement of said members within said corresponding resonators, said inductive portion of each member alfecting the inductance of a corresponding resonator resulting from the flow of induced circulating electric current about the periphery of said inductive portion, said capacitive portion of each of said members having a longitudinally disposed discontinuity for reducing the flow of electric current about the periphery of said portion until the capacitance between corresponding ones of said members and said resonators predominates over the afore said inductance. A

I 4. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators each having a predominantly capacitive region adjacent one end thereof and a predominantly inductive region adjacent the other end thereof, a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure, means for effecting movement of said members within said predominantly inductive region of corresponding resonators, said members each having a longtudinally disposed discontinuity of a length less than the depth of said cavity resonators and extending over a portion adjacent one end thereof for substantially reducing the flow of electric current about the periphery of said portion.

5. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators each havinga predominantly capacitive region adjacent one end thereof and a predominantly inductive region adjacent the other end thereof, a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure, means for effecting movement of said members within said predominantly inductive region of corresponding resonators, a portion of each of said members adjacent one end thereof being of tubular crosssection and containing a longitudinally disposed slot, the remainder of each of said members having a continuous periphery.

6. An electron discharge device comprising a cathode, an anode structure spaced from said cathode and includ ing a plurality of segments, said anode structure at least partially defining a multiplicity of cavity resonators, a plurality of conductive straps interconnecting certain ones of said anode segments on both sides of said anode structure, a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure, means for effecting movernent of said members within said corresponding resonators, said members each having a longitudinally disposed discontinuity extending over a portion adjacent one end thereof for substantially reducing the flow of electric current about the periphery of said portions, the remainder of each of said members having a continuous periphery, said members further being positioned a substantial distance from said straps.

7. An electron discharge device comprising a cathode, an anode structure spaced from said cathode and including a plurality of segments, said anode structure at least partially defining a multiplicity of cavity resonators each having a predominantly capacitive region adjacent one end thereof and a predominantly inductive region adjacent the other end thereof, a plurality of conductive straps interconnecting certain ones of said anode segments on both sides of said anode structure, a tuning structure including a plurality of axially extending electrically conductive members supported adjacent said anode structure, means for effecting movement of said members within said predominantly inductive region of corresponding resonators, said members each having a longitudinally disposed discontinuity extending over a portion adjacent one end thereof for substantially reducing the flow of electric current about the periphery of said portions, the remainder of each of said members having a continuous periphery, said members further being positioned a substantial distance from said straps.

8. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators each having a predominantly capacitive region adjacent the one end thereof and a predominantly inductive region adjacent the other end thereof, a tuning structure including a plurality of axially extending electrically conductive members each containing a longitudinal slot extending over a limited portion adjacent one end thereof, means for effecting movement of said members Within said predominantly inductive region of corresponding resonators, means responsive to insertion of said slotted portion only of each of said members within corresponding resonators for producing a variation in the impedance of said resonators which is principally capacitive.

9. An electron discharge device comprising a cathode, an anode structure spaced from said cathode, said anode structure at least partially defining a multiplicity of cavity resonators, a tuning structure including a plurality of axially extending electrically conductive members each containing a longitudinal slot extending over a tubular portion adjacent one end thereof, means for effecting movement of said members within said correspond ng resonators, means responsive to insertion of said slotted portion only of each of said members within corresponding resonators for producing a variation in the impedance of said resonators which is principally capacitive.

10. An electron discharge device for generating radio frequency energy comprising a cathode, an anode spaced from said cathode, a pair of oppositely positioned means for establishing a magnetic field between said cathode and said anode which is substantially normal to the electric field between said cathode and said anode, said anode structure at least partially defining a plurality of cavity resonators, said electric and magnetic fields combining to produce a radio frequency current flowing about the eripheries of said cavity resonators, and a tuning structure including a plurality of axially extending electrically conductive members each having a first portion and a second portion, means for effecting movement of said first and second portions of each member within said corresponding resonators in the order named, means responsive to the insertion of said second portion of said members within corresponding resonators for inducing therein a peripheral radio frequency current, said first portion of said members having a peripheral discontinuity therein.

11. An electron discharge device for generating radio frequency energy comprising a cathode, an anode spaced from said cathode, a pair of oppositely positioned means for establishing a magnetic field between said cathode and said anode which is substantially normal to the electric field between said cathode and said anode, said anode structure at least partially defining a plurality of cavity resonators each having a predominantly capacitive region relatively adjacent said cathode and a predominantly inductive region relatively remote from said cathode, said electric and magnetic fields combining to producea radio frequency current flowing about the peripheries of said cavity resonators, and a tuning structure including a plurality of axially extending electrically conductive members each having a first tubular portion and a second portion, means for effecting movement of said first and second portions of each member within said inductive region of said corresponding resonators in the order named, means responsive to the insertion of said second portion of said members within corresponding resonators'for inducing therein a peripheral radio frequency current, said tubular first portion of said members having an elongated longitudinal slot therein for preventing the induction therein of an electric current.

12. An electron discharge device for generating radio frequency energy comprising a cathode, an anode spaced from said cathode, a pair of oppositely positioned means for establishing a magnetic field between said cathode and said anode which is substantially normal to the electric field between said cathode and said anode, said anode structure at least partially defining a plurality of cavity resonators each having a predominantly capacitive re gion relatively adjacent said cathode and a predominantly inductive region relatively remote from said cathode, said electric and magnetic fields combined to produce a radio frequency current flowing about the peripheries of said cavity resonators, and a tuning structure including a plurality of axially extending electrically conductive members each having a first tubular portion and a second portion, means for effecting movement of said first and second portions of each member within said inductive region of said corresponding resonators in the order named, means responsive to the insertion of said second portion It of said members Within corresponding resonators for inducing therein a peripheral radio frequency current, said tubular first portion of said members having a peripheral discontinuity therein, means responsive to insertion of said first portion of said members within corresponding resonators for effecting the capacitance of said resonators.

No references cited. 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING A CATHODE, AN ANODE STRUCTURE SPACED FROM SAID CATHODE, SAID ANODE STRUCTURE AT LEAST PARTIALLY DEFINING A MULTIPLICITY OF CAVITY RESONATORS AND A TUNING STRUCTURE INCLUDING A PLURALITY OF AXIALLY EXTENDING ELECTRICALLY CONDUCTIVE MEMBERS SUPPORTED ADJACENT SAID ANODE STRUCTURE AND MOVABLE WITH RESPECT THERETO, SAID MEMBERS EACH HAVING AN INDUCTIVE PORTION AND A CAPACITIVE PORTION FORMING AN EXTENSION OF SAID INDUCTIVE PORTION. 